Method of making retractile cords



Jan. 18, 1944. T. K. cox

METHOD OF MAKING RETRACTILE CORDS Filed June 5, 1940 ATTORNEY junctionUNITED STATES- PATENT OFFICE .Y -ME'IIIOD 0F MAKING BE'PRAOTILE CGBDSA'l-'lloma' IL'Cox,l Randallstown, Md.,l asslgnor to Western ElectricCompany, Incorporated, New York, N. Y., a corporation of New YorkApplication June 5, 194e, serial No. 338,881

z claims. This invention relates to a method of making a retractile cordand .more particularly to a'method of making a rubber covered retractilecord. u In vthe manufacture of rubber covered retractile cordsconsiderable dimculty vhas been experi-v enced in many cases invulcanizing a retractile cord in such a manner that the covering willnot be distorted and the adjacent convolutions of the cord will notadhere together.

An object of the present invention is to provide an eilective andeflicient method of making a rubber covered retractile cord.

In accordance with one embodiment of the invention a rubber covered cordis iirst made in a continuous vulcanizing apparatusand vulcanized to asubstantial degree. length of such a vulcanized cord is wound in helicalform upon a'mandrel in which form the vulcanization is continued to setthe the desired form.

A complete'understanding of the nature and embodiment of the inventionwill be had by reierence to the following description taken in conwiththe accompanying drawing, in

which Fig. 1 is a side elevation of a continuous vulcanizing apparatuswhich may be used in practicing the invention and Fig. 2 is adetail viewof a' section of a rubber covered,cord wound on a mandrel for furthervulcanization.

'I'he apparatus which may be used in practising the invention isprovided with a supply reel II from which one or :more wires l2, to becovered, are drawn through a wire straightening device l3, of anydesired form, by means of a capstan Il around. which the wire passes,the capstan being driven through a pulley I5 by'means oi.' a belt I6connected to a suitable source of power (not shown) at a speed slightlygreater than that of the wire to relieve tension on the rubber inoctober 13, 192s. 1n the vulcanizing chamber the rubber covered'cord maybe vulcanized to a vulcanized if vno further heat treatment wereThereafter a suitable wire duringgit's passage through the vulcanzingchamber. From the capstan the wire 'or wires vpass through a head I8 ofan extrustion mech-- anism which is adapted toextrude a uniform coatingo! vulcanized insulating material on the wire or wires `as they emergefrom the extru-v sion mechanism I8. From the extrustion'head .about 60lbs. per square inch to vulcanize the cord. The details of thismechanism will not' be described herein since they are fully disclosedin the patent to L. F. Lamplough, No. 1,689,295,

contemplated, although a lesser degree of 'vulcanization in this stepmay be used so long as the cord is vulcanized to such an extent that therubber will notbe readily distorted or adhere to ad- I jacent rubbersurfaces upon furthervulcanization. From the `vulcanizing chamber a cordpasses through a seal 23 around a s'heave 24 to a takeup capstan 25driven through a pulley 26 from a belt 21 connected to any suitablesource of power (not shown). From the take-up capstan 25 the cord may bewound upon a take-up reel 28. Sufcient time elapses during the travel ofthe cord around the sheave 24 and the capstan 25 for the insulatingmaterial to cool suiiiciently to be wound on the takeup reel 28.

The second step of the invention comprises takingv a suitable length ofthe rubber covered cord from -a reel and Winding it upon a mandrel 29.Suitable clips 3| may be provided on the mandrel for holding the ends ofthe cord. The end of the mandrel is shown provided with a gear 32 bymeans of which the mandrel may be rotated in a suitable mechanism (notshown) when winding the cord on the mandrel. yA cordv or number of cordlengths thus wound upon the mandrel are then placed in a vulcanizingchain lpermanent set of the cord into helical form. Satisfactory resultshave been obtained by vulcanizing the cord on a mandrel for a period often minutes. After heat treating the cord is cooled on the mandrel andafter being cooled may be removedand it will yieldingly retain a helicalform sol thatv when a longitudinal tension is applied it will stretch,and retract when the tension'is released. The retractility of the cordmay be enhanced by winding Athe cord of a larger pitch, that is byleaving spaces between adjacent convolutions, then after the nalvulcanization of the -cord one end of the cord may be drawn through thehelix' to invert the cord. In this manner the retractility of the cordmay be increased to such an extent that a Vdefinite pressure is exertedbetween the adjacent convolutions.

It will be understood that the nature and embodiment of the inventionherein described is merely illustrative and that many changes and thecord into a helical, retractile form, and heatl0 ing the cord to set thecord in said form.

2. A method of making a retractile cord which comprises heating aconductor coated with vulcanizable material to cure the material, coilngthe cord thus formed into a helical, retractile form, and heating saidmaterial to set the cord in said form.

THOMAS K. COX.

